Reverse flow spin-cleaning liquid filters

ABSTRACT

In a liquid filter of the reverse-flow flush-cleaning type, the present invention provides the improvement of mounting the pack of discs ( 170 ) intermediate an assembly comprising a seat member ( 200 ) and screw-thread split-ring ( 202 ).

BACKGROUND OF THE INVENTION

The present invention relates to liquid filters, particularly for waterirrigation systems, however also useful for other industrial or domesticapplications.

More specifically, the invention concerns filter devices of the typedisclosed in our U.S. Pat. No. 6,398,037 issued Jun. 4, 2002 which ishereby incorporated by reference (hereinafter called “the Patent”).

The Patent relates to filter devices utilizing a battery of filter discswith reverse flushing water flow cycles wherein the discs were caused tospin under the impact of water jets impinging thereon (hereinafterreferred to as “Spin-Clean Filters”).

For better understanding of the invention herein disclosed, referenceshall be made to FIG. 1 which depicts the reverse flow spin-cleaningstage of the filter device (conforming FIG. 10 of the Patent except thatthe spin-cleaning stage is provoked by the reverse flow proper ratherthan by an external pressure command, a feature which is understood tobe encompassed within the scope of the Patent).

Using the same reference numerals as in the Patent, the water (or otherliquid) admitted through the outlet port 20 flows into the conduit 30 a(and conduits 30 b and 30 c that are not shown) and, through an opening102 a (not existing in the Patent exemplified embodiment) into thecylinder space 40 of the cylinder-and-piston assembly 28. Under apressure sufficient to overcome the force of the spring 52, the piston58 along with the cap member 60 will slide towards the distal end of thefilter 10, relieving the clamping of the filter discs battery 70. Thestroke of piston 58 is delimited by a protrusion 104 formed at thehousing member 12 (shown but not referenced in the Patent drawings). Aswill be explained later on, this need for an extra, exterior element forstopping the progress of the piston has been found disadvantageous andhence remedied by one aspect of the present invention.

Turning now to the proximal end of the filter device 10, there has beenused a female screw-threaded ring portion 38 of the fixed member againstwhich the filter discs are pressed for mounting the integral main filtercore member 24 to the filter housing structure 14 intermediate femalescrew-threaded ring 82. This mounting or coupling arrangement has alsobeen found worthy of improvement as will be explained in detail below.

SUMMARY OF THE INVENTION

Thus provided according to one aspect of the invention is a liquidfiltering device, particularly for irrigation water installationscomprising a cylindrical housing with an inlet port and an outlet port;a cylindrical filter member installed within the housing so that, waterflowing from the inlet port to the outlet port enters the filter memberin a radial direction, and is discharged through the outlet port, andvice-versa during reversed, filter flushing flow cycles; a core membercentrally mounted within the cylindrical space defined by, and forming asupport for, the filter member; a fixed member abutting against thefilter member at one axial end thereof; a piston assembly mounted to thecore member comprising a piston and a displaceable member coupled to thepiston and abutting against the filter member at the other axial sidethereof; wherein said mounting of the core member comprises a femalescrew-thread forming part of the said fixed member; a femalescrew-threaded split ring matching the female screw-thread; and acircular convergent cone shaped trough encompassing the ring fixedlymounted to said housing; the arrangement being such that upon threadingtogether, the ring becomes attracted towards the fixed member and thusself-tightened by frictionally clamping within the cone-shaped trough.

According to another aspect of the invention, the piston assembly isprovided with means for limiting the progress amount of the piston, suchas a coil spring, the number and size of the coils being designed so asto limit the stroke of the piston following a predetermined compressionthereof.

BRIEF DESCRIPTION OF THE DRAWINGS

These and additional constructional features and advantages of thepresent invention will become more clearly understood in light of theensuing description of a preferred embodiment thereof, given by way ofexample only, with reference to the accompanying drawings, wherein:

FIG. 1 is a longitudinal cross-sectional view of the filter device ofthe Patent in reverse flush flow, spin-cleaning mode of operation;

FIG. 2 is a cross-sectional view of a filter device incorporating theimprovements of the preset invention;

FIG. 3 shows the split-ring before assembly;

FIG. 4 shows the seat member of the split-ring;

FIG. 5 shows the split-ring in the preparatory state for insertion intothe seat member;

FIG. 6 shows the assembled state of the split-ring;

FIG. 7 a is a partial cross-section showing the initial state ofengagement of the core coupling ring and the split-ring;

FIG. 7 b shows the final state of engagement;

FIG. 8 is a schematic view of a group of filter devices installed inparallel; and

FIG. 9 is a schematic view of several filter devices installed inseries.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As clearly seen in FIG. 2, the mounting of the filtering discs battery170 to the inlet/outlet housing member 114 has been modified. Ratherthan female screw-threaded ring 82 (FIG. 1) there is provided anassembly comprised of seat member 200 and screw-threaded split-ring 202shown in more detail in FIGS. 3-7.

The seat member 200 is formed with a circular trough portion defined bycircular rim 200 a, convergent cone-shaped wall 200 b and planar radialwall 200 c.

The seat member 200 is shown as integrally formed with the outletfitting but other variations may be employed such as by welding.

The ring 202 is split as shown and made of an elastic or springymaterial to allow its closing by force (FIG. 5) into a reduced diameterwhich must be smaller than the opening defined by the rim 200 a.

The outer surface 202 a of the ring 202 is beveled by the same angle asthe seat cone wall 200 b. The inner side is provided with a screw-threadmatching that of the core member ring 138.

The height of the ring 202 is less than the distance between the innersurfaces of the rim 200 a and of the radial wall 200 c.

The mounting of the core member 124 is perfected in the followingmanner. First, the split-ring 202 is inserted into the trough portion byforcing it to close and placing thereinside, whereupon the ring willresume its partially open state (FIG. 7 a). It is designed so that inthis position the screw threads of the ring 138 and of the split-ring202 will match.

Upon relative rotation, the split-ring becomes dragged along thecone-shaped wall 200 b up to a certain point (FIG. 7 b). Consequently, aself-tightening effect occurs whereby a highly secured and sealedcoupling of the threaded members to each other is attained in a moreeffective way than in the Patent construction (FIG. 1).

If necessary, stop means such as projection 200 d may be provided toavoid the unison rotation of the two parts, at-least at the beginning ofthe operation where the friction between the beveled ring portions 202 aand the seat wall portion 200 b might be insufficient.

The dismantling of the core member 124 from the seat member 200 formaintenance or replacement purposes follows in the reverse order.

Turning now to the distal side of the filter device 110, it will bereadily seen that, by properly choosing the number and diameter of thecoils, the spring 252 functions as an autonomic stop, limiting thestroke of the piston 158 (and cap member 160).

This seemingly minor and even almost obvious modification presents,however, the advantage of completely dispensing with the stop cap(104—FIG. 1). Moreover, the length of the piston stroke can be governedand properly selected irrespectively of the housing(s) size.

This variability becomes even more significant where the filter devicesare used in groups, either in parallel or in series.

In FIG. 8 a battery of five filter devices 310 is shown (only three areseen) operating in parallel. The filters are mounted on a common baseformed in inlet/outlet housing member 314, either by the arrangementdescribed above or otherwise.

Noteworthy in the present context is that the cylinder and pistonassemblies 328 incorporate the integral piston-stroke limiting meansrather than external stop-by-abutment means (cap 104 in FIG. 1). Thisentails a significant saving in the design and structure of the otherhousing member 312.

The filter devices 410 of FIG. 9 operate in tandem between the commoninlet and outlet, e.g. to achieve superfine quality of filtered liquid.

This type of construction is only enabled by implementation of theself-limiting piston-stroke means proposed according to the presentinvention.

Those skilled in the art to which this invention pertains will readilyappreciate that numerous changes, variations and modifications can beeffected without departing from the true spirit and scope of theinvention as defined in and by the appended claims.

1. A liquid filtering device, particularly for irrigation waterinstallations comprising: Housing with an inlet port and an outlet port;a core member centrally mounted within the housing comprising at oneaxial end thereof an abutment ring associated with a male screw-threadfor mounting the core member to the housing next to and in communicationwith the inlet port; a discs-type filter member supported by thecore-member so that water flowing from the inlet port enters the filtermember in a radial direction, and is discharged through the outlet port,and vice-versa during reversed, filter flushing flow cycles; a pistonassembly mounted to the core member comprising a piston and adisplaceable member coupled to the piston and abutting against thefilter member at the other axial side thereof; characterized in that themounting of the core member comprises a female screw-threaded split ringmatching the male screw-thread; and a circular convergent cone shapedtrough encompassing the split ring and fixedly mounted to housing, thearrangement being such that upon threading together, the split-ring isattracted towards the abutment ring and thus becomes self-tightenedagainst the cone-shaped wall of the trough.
 2. The device as claimed inclaim 1 wherein the said trough is open at at-least one side thereofallowing the split ring to be inserted thereinto by elasticallysqueezing same into a smaller diameter.
 3. The device as claimed inclaim 2 wherein the said trough is integrally formed with a fittingcommunicating the core member with the inlet port of the filter member.4. The device as claimed in claim 3 wherein a stop is provided withinthe trough for avoiding free rotation of the split ring.
 5. The deviceas claimed in claim 1 wherein the piston assembly is provided with meansfor limiting the progress amount of the piston.
 6. The device as claimedin claim 5 wherein said means comprise a coil spring, the number andsize of the coils being designed so as to limit the stroke of the pistonfollowing a predetermined compression thereof.
 7. The device as claimedin any of claims 1-6 in use as one of a plurality of filter devicesoperating in parallel.
 8. The device as claimed in any of claims 1-6 inuse as one of a plurality of filter devices operating in series.